Reactive power compensation device at tail end of ship emergency fire pump

Abstract

The invention belongs to the related technical field of ship manufacturing, and particularly discloses a reactive power compensation device at the tail end of a ship emergency fire pump, which comprises two groups of capacitors with different capacities, the capacitors are respectively marked as high-capacity capacitors and low-capacity capacitors according to the capacities, and each group of capacitors is provided with a built-in reactor and a corresponding protection fuse. Two circuit breakers, two contactors and a time relay are also configured; the capacity of a small-capacity capacitor is calculated according to the power factor of the emergency fire pump in normal operation and the target power factor, the compensation value of the small-capacity capacitor is determined through the capacity of the small-capacity capacitor, and when the power factor of the emergency fire pump is compensated to the target power factor when the motor is started, the compensation value of the small-capacity capacitor is subtracted. And calculating to obtain the capacity of the high-capacity capacitor.

Description

Technical Field

[0001] The invention relates to the technical field related to shipbuilding, and in particular to a reactive power compensation device at the terminal of a ship emergency fire pump. Background Art

[0002] Conventional star-delta started ship emergency fire pumps are at risk of starting failure during ship mooring, sea trials and operation. To address the problem of possible starting failure of ship emergency fire pumps, the main solutions are: first, adjust the starting circuit protection setting parameters to avoid motor starting current and starting impact current; second, replace the starter from a conventional star-delta starter with other types of starters with smaller starting current, such as closed star-delta starters, autotransformers, soft starters and even variable frequency starters; third, directly connect a capacitor in parallel at the end of the emergency fire pump power supply circuit for on-site reactive power compensation.

[0003] Solution 1 avoids the starting current and starting impact current by adjusting the setting parameters of the starting circuit. It has the advantages of easy adjustment and no hardware cost. However, the starting impact current occurs at the moment of motor starting or during the star-delta conversion process, and the duration is very short and difficult to measure. The protection setting parameters of the motor include undervoltage protection, overload protection, short delay protection, long delay protection and short circuit protection, which are difficult to set. During the ship's sea trial or operation, the technicians may not have the ability and conditions to adjust the protection setting parameters. Improper adjustment may cause the switch to malfunction or even cause the grid to be disconnected. At the same time, the circuit breaker of the general protection circuit is selected according to the rated current of the motor, and the protection setting value of the matching release can only be adjusted within a certain range. It is possible that even if it is adjusted to the maximum, it cannot avoid the starting impact current.

[0004] The main disadvantage of Option 2 is the high cost. Since the probability of a ship emergency fire pump starting failure is not high, a star-delta starter is usually selected in the design phase for cost considerations. If a starter with better starting performance is used in the design phase, the ship construction cost will be increased. If there are no spare parts available when a start failure occurs during the ship's mooring, sea trials, and operation, the problem cannot be solved in a timely manner.

[0005] Solution 3 directly connects capacitors in parallel with the motor for reactive power compensation, which has a simple structure and low cost. Its main disadvantage is that the power factor is difficult to predict during the motor starting process, and the power factor of the emergency fire pump is generally stable between 0.7 and 0.9 during stable operation. If the parallel capacitor is too large, it will cause overcompensation and overvoltage after the start-up. If the parallel capacitor is too small, the reactive power compensation is insufficient and the starting current and starting impact current cannot be effectively reduced. Group switching capacitors or static reactive power compensators usually have large capacity and high cost. They are usually used for centralized compensation and decentralized compensation on the grid side, and are generally not used for terminal compensation.

[0006] In view of this, the present invention provides a reactive power compensation device for a terminal of a ship emergency fire pump. Summary of the invention

[0007] The purpose of the present invention is to provide a reactive power compensation device at the end of a ship emergency fire pump, which is configured according to the power factor of the motor during the starting process for the capacitor directly connected in parallel at the end of the motor. After the starting is completed, over-compensation may cause overvoltage.

[0008] To achieve the above object, the present invention provides the following technical solution: a terminal reactive power compensation device for a ship emergency fire pump, comprising two groups of capacitors with different capacities, which are marked as large-capacity capacitors and small-capacity capacitors according to their capacities.

[0009] Each group of capacitors is equipped with a built-in reactor and corresponding protective fuses, two circuit breakers, two contactors and a time relay;

[0010] The capacity of the small-capacity capacitor is calculated based on the power factor and target power factor during normal operation of the emergency fire pump, and the compensation value of the small-capacity capacitor is determined by the capacity of the small-capacity capacitor. When the power factor of the emergency fire pump at motor start-up is compensated to the target power factor and the compensation value of the small-capacity capacitor is subtracted, the capacity of the large-capacity capacitor is calculated.

[0011] As a preferred technical solution of the present invention, a large-capacity capacitor C1 and a small-capacity capacitor C2 are connected in parallel to the outlet of the emergency fire pump, and a protective fuse and a contactor are connected to the circuit to disconnect the circuit in time.

[0012] As a preferred technical solution of the present invention, when the emergency fire pump is not working, the contactor KM1 is closed, the contactor KM2 is disconnected, and the reactor capacitor is connected to the emergency switchboard for centralized reactive power compensation;

[0013] When the emergency fire pump is started, contactor KT1 is activated, contactor KM2 is closed, contactor KM1 is disconnected, inductor L1, capacitor C1 and inductor L2, capacitor C2 are connected in parallel at the outlet of the emergency fire pump for reactive power compensation;

[0014] After the start-up is completed, the timing of the time relay KT1 ends, the contactor KM2 is disconnected, the contactor KM1 is closed, the inductor L1 and the capacitor C1 continue to perform centralized reactive power compensation for the emergency distribution network, and the inductor L2 and the capacitor C2 continue to be connected in parallel to the emergency fire pump for terminal compensation.

[0015] As a preferred technical solution of the present invention, overload and short-circuit protection are provided by circuit breakers and fuses; a time relay is used to control the closing and opening of the contactor to achieve automatic switching of the compensation strategy.

[0016] As a preferred technical solution of the present invention, a monitoring system is provided to monitor the power factor and current, and the capacity or control logic of the capacitor is fine-tuned according to the actual operating conditions.

[0017] As a preferred technical solution of the present invention, a PLC programmable logic controller is used to dynamically adjust the switching of capacitors using real-time data.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention aims at the risk of starting failure of the ship emergency fire pump during the ship mooring, sea trial and operation. It is composed of two groups of capacitors, one large and one small. When the emergency fire pump is started, reactive power compensation is performed together. When the emergency fire pump starts and ends normal operation or stops running, the large group of capacitors is connected to the ship emergency distribution network to perform centralized reactive power compensation for other loads, and the small group of capacitors performs terminal reactive power compensation for the normally running emergency fire pump. The ship emergency distribution board is connected outside the motor starting time to improve the power factor of the emergency distribution network, improve the utilization rate of the emergency generator, and also improve the power supply capacity of the emergency distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of reactive power compensation at the terminal of a ship emergency fire pump;

[0021] Figure 2 This is the circuit schematic diagram of the reactive power compensation device at the end of the ship emergency fire pump; DETAILED DESCRIPTION

[0022] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0023] In this embodiment, the terminal reactive power compensation is performed by locally connecting capacitors in parallel with the motor. If the capacitors directly connected in parallel with the motor terminals are configured according to the power factor during the motor starting process, over-compensation may occur after the starting is completed, resulting in overvoltage. If the capacitor is too small, insufficient reactive power compensation will result. Group switching or static reactive power compensators are not suitable for terminal compensation. The proposed terminal reactive power compensation device for the emergency fire pump of a ship can perform reactive power compensation when the emergency fire pump is started, limit the starting current and the starting impact current, and avoid the failure of the emergency fire pump to start. When the emergency fire pump is started, the emergency fire pump is compensated for reactive power on site, and the emergency power supply system is compensated for reactive power in a centralized manner. If the emergency fire pump is not running, the emergency power supply system can also be compensated for reactive power in a centralized manner.

[0024] See also Figure 1-2 The present invention provides a reactive power compensation device at the terminal of a ship emergency fire pump, comprising a reactive power compensation device, one end of which is connected in parallel with the outlet terminal of the emergency fire pump, and the other end is connected to the emergency switchboard; the reactive power compensation device comprises two groups of built-in reactor capacitors and protective fuses, and the protective fuses are respectively connected to the emergency fire pump and the emergency switchboard through a circuit breaker;

[0025] Specifically, the reactor-type capacitor is composed of a capacitor and an inductor connected in series, and two groups of capacitors with different capacities are marked as large-capacity capacitor C1 and small-capacity capacitor C2 according to their capacities; each group of capacitors is equipped with built-in reactors L1 and L2, and corresponding protective fuses FU1 and FU2; two circuit breakers QF1 and QF2, two contactors KM1 and KM2, and a time relay KT1 are configured.

[0026] The reactor-type capacitor includes a first reactor-type capacitor composed of a capacitor C1 and an inductor L1, and a second reactor-type capacitor composed of a capacitor C2 and an inductor L2; the protective fuses include FU1 and FU2, the circuit breakers include QF1 and QF2, and the circuit breakers play a protective role; the contactors include KM1 and KM2, and the time relay KT1; its built-in reactor has the functions of limiting the high-order harmonic current flowing into the capacitor, suppressing harmonic amplification and reducing the inrush current of the river gate.

[0027] Specifically, the capacity of the small-capacity capacitor is calculated based on the power factor and target power factor during normal operation of the emergency fire pump, and the compensation value of the small-capacity capacitor is determined by the capacity of the small-capacity capacitor. When the power factor of the emergency fire pump at motor start-up is compensated to the target power factor and the compensation value of the small-capacity capacitor is subtracted, the capacity of the large-capacity capacitor is calculated.

[0028] More specifically, the reactive power calculation formula that the reactive power compensation device needs to compensate is:

[0029]

[0030] Among them: C2 compensates the normal operating power factor of the emergency fire pump from about 0.7 to 0.9, Q C2 ≈0.5P e , C1 is compensated to 0.9 according to the power factor of about 0.3 when the motor starts, minus the compensation value of C2, Q C1 ≈2.2P e .

[0031] When the emergency fire pump is not working, the normally closed contact of KM2 and the coil circuit of KM1 are connected, the contactor KM1 is closed, KM2 is disconnected, and L1 and C1 are connected to the emergency distribution board, which plays the role of centralized reactive power compensation for the emergency distribution network.

[0032] When the emergency fire pump starts to start, the normally closed coil of timer KT1 and the KM2 coil circuit are connected, the contactor KM2 is closed, the normally closed contact of KM2 and the KM1 coil circuit are disconnected, and the contactor KM1 is disconnected. At this time, L1, C1 and L2, C2 are connected in parallel at the outlet of the emergency fire pump.

[0033] When the emergency fire pump is started, the timer KT1 circuit is connected, the timer KT1 normally closed coil and the KM2 coil circuit are disconnected, the contactor KM2 is disconnected, the KM2 normally closed contact and the KM1 coil circuit are connected, the contactor KM1 is closed, KM2 is disconnected, L1 and C1 are connected to the emergency distribution board, and the emergency distribution network continues to be centrally compensated for reactive power. L2 and C2 continue to be connected in parallel to the emergency fire pump for terminal compensation.

[0034] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art who is familiar with the technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

[0035] Finally: The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A reactive power compensation device for a terminal of a ship emergency fire pump, characterized in that: It includes two groups of capacitors with different capacities, which are marked as large-capacity capacitors and small-capacity capacitors according to their capacities. Each group of capacitors is equipped with a built-in reactor and corresponding protective fuses, two circuit breakers, two contactors and a time relay; The capacity of the small-capacity capacitor is calculated based on the power factor and target power factor during normal operation of the emergency fire pump, and the compensation value of the small-capacity capacitor is determined by the capacity of the small-capacity capacitor. When the power factor of the emergency fire pump at motor start-up is compensated to the target power factor and the compensation value of the small-capacity capacitor is subtracted, the capacity of the large-capacity capacitor is calculated.

2. A reactive power compensation device for terminal of a ship emergency fire pump according to claim 1, characterized in that: The large-capacity capacitor C1 and the small-capacity capacitor C2 are connected in parallel at the outlet end of the emergency fire pump, and the protection fuse and contactor are connected to the circuit to disconnect the circuit in time.

3. A reactive power compensation device for terminal of a ship emergency fire pump according to claim 2, characterized in that: When the emergency fire pump is not working, contactor KM1 is closed, contactor KM2 is disconnected, and the reactor capacitor is connected to the emergency switchboard for centralized reactive power compensation; When the emergency fire pump is started, contactor KT1 is activated, contactor KM2 is closed, contactor KM1 is disconnected, inductor L1, capacitor C1 and inductor L2, capacitor C2 are connected in parallel at the outlet of the emergency fire pump for reactive power compensation; After the start-up is completed, the timing of the time relay KT1 ends, the contactor KM2 is disconnected, the contactor KM1 is closed, the inductor L1 and the capacitor C1 continue to perform centralized reactive power compensation for the emergency distribution network, and the inductor L2 and the capacitor C2 continue to be connected in parallel to the emergency fire pump for terminal compensation.

4. A reactive power compensation device for terminal of a ship emergency fire pump according to claim 3, characterized in that: Overload and short-circuit protection is provided by circuit breakers and fuses; time relays are used to control the closing and opening of contactors to achieve automatic switching of compensation strategies.

5. A reactive power compensation device for terminal of a ship emergency fire pump according to claim 4, characterized in that: Set up a monitoring system to monitor the power factor and current, and fine-tune the capacitor capacity or control logic based on actual operating conditions.

6. A reactive power compensation device for terminal of a ship emergency fire pump according to claim 5, characterized in that: Use PLC programmable logic controller real-time data to dynamically adjust the switching of capacitors.

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